Method of making sheet metal flume troughs



Dec. 5, 1933. C NORTON 1,937,663

METHOD OF MAKING SHEET METAL FLUME TROUGHS Filed April 30, 1932 2 Sheets-Sheet 1 INVENTOR, 5166a CLLLCC wort; BY v- ATTORNEYS.

Dec. '5, 1933. A N 'RTON 1,937,663

METHOD OF MAKING SHEET METAL FLUME TROUGHS Filed April 30, 1932 2 Sheets-Sheet 2 INVENTOR,

ATTORNEYS.

, g approaches the maximum. 1

Patented Dec. 5, 1933 I I I I v I o U D: TATES 'PAT Nu- .oFEic-a .1

1,937,663 METHOD OF MAKING SHEET METAL i J TROUGHS Albert Colwell Norton, Berkeley, Calif., assignor to California Corrugated Culvert 00., Berkeley, Calif., acorporation of California 1 Application Apr-i130, 1932 Serial No. 608,396

'5 Claims. (01. 153-32) The present invention relates to the manufacwithin the limits of the claims hereto appended, ture of sheet metal troughs used in flumes for without departing from the spirit of the inventhe transportation of water. tion as defined in said claims. Sheet metal flume troughs are commonly In the drawings: i J I v formed initially to semicircular cross section. It Fig. 1 is a, transverse section of a trough 5o is Well known in the art, however, that such cross formed accordingto my invention. section is distorted under load, and tendsto as- V Fig, 2 is a diagram illustrating the layout of sume a curvature corresponding approximately the compound curve uponwhich the trough is to the'hydraulic catenary.. Such distortion is formed, and showing the deflection from the 1 resisted to some extent by the stiffness of the semicircle and the limitsthereof'under varying :5 sheet metal, and still more "by .thesuspending loads. .7 V I rods and the'transverse joints between adjacent Figs. 3- and +1 are diagrammatic endvelevations trough sections, said joints usually including both illustrating respectively;the-successive v steps in transverse beads formed in the metal of the my improved method of forming the trough-to 5 trough section. and transverse clamping rods. the compound curve shown inFig. 2. A 70 v The curvature of the trough also changes with l Referringmore particularly to the drawings, variationsin load, the deflection from the semithe reference numeral 1-designates a; trough circle being greatest when the trough is about formed from sheetmetal withra rounded bottom half full of water, and-decreasing as the load 2 anddivergent'sides 3; the latter being curved I r 1 inwardly upon a radius'greater than that of 75 Distortion of initially semicircular flumes has said bottom; The trough is suspended by rods, caused much, annoyance and expense by produoone of which isshown at 4, extendingtransverseing' leaks at the joints, especially at the ends of 1y beneath it, the ends of'said'rodsbeing secured the fiume, where the sheet-metal trough joins to the frame or substructuraa conventional form 5 rigid structures such as concrete head Walls. of which iS Sh0Wl.1;inFlg. 1 comprising longig0- Attempts havebeen made to overcome this leaktudinal stringers 5 and cross bars 6.. In my. image by. forming the concrete structure to a the:- proved construction, the upper portions; of the oretical .catenary curvature where it is in; consides 3 of the trough diverge at anglesof about tact with the sheet metaLt-rough. Such attempts 16 degrees fromthe vvertical, and theupper'end c 0 have not been successfuLbecauseof the fact that portions of the rods 4, where they are attached 5 the curvature assumed by, the loadedtrough is to the frame, are also positioned at the same not a true catenary, and-cannot be calculated angle, I i v g i .l by any mathematical iormulaheretofore known. My trough 1 is formed of any'suitable metal, I have found it possible to overcome the diifipreferably galvanized sheet steel of, theweight 5 ,culties'inherent inthe semicircular sheet metal and stiffness ordinarily used in "such structures. 9o

flume, and to prevent leakage and loosening of Its cross sectional shape is a compound curve the joints and suspension rods, by forming the drawn about three major centers, with narrow trough initially to a curve which may be defined transition areas of changing radius connecting broadly as the mean between the limits of disthe major arcs. In the theoretical consideration 40 tortion caused by variations in load, and which of the curve, these transition areas may bleflige 95 ca laid'out a u hr maj r cent rs Whos nored, however. The curve and its mathematical positions may be expressed as functions of the layout are illustrated diagrammatically-in Fig.2, width across the top of the trough. I have also in which the heavy solid line 1a is the curve upon 1 developed a simple and inexpensive method of which'the trough 1 is formed, 2a being the central formingthe sheet to'the p u cu ve above are of-shorter radius and 3a the side rcseof 100 described,all-of which results in a fiumesupe- I longer radius, corresponding respectivelyv to the rior to those now in use. I The employment of a bottom 2 and sides 3 of the trough, The-Mcurvelasheet metal trough of compound curvature also is constructed asfollowsz H enables me to make important economies in the Upon a horizontal line "d-,,-d whose length D1.

supporting substructure, as described and claimed is the desired width across the top; of the trough, I05

in my United States Letters Patent 1,878,289for construct a semicircle with Das' its diameter, as Plumes. a 7 I shownby the light solidlineb; The-length of My invention willnow be described in detail said semicircle, i. e. one half the circumference withf'reference to theaccompanying drawings, it of, ajcirclewhose diameter is1D,fo r 1.57 08,-D,will j v being understoodthat changes, maybe made, be: the widthoi the sheet fromwhich the trough 11.0

. center line being approximately equal to 0;3l7D, and theirvertical distance B above the horizontal line being approximately equal to 0173B. Using the points 0 as centers, and the greater distance 0d, or R, as radius, draw arcs 3a downwardly.

from the line dd; The distance 0d, or R, is approximately equal to 0.834 D, and is the radius of curvature of the divergent sides 3 of the trough. Now locate 0 upon the vertical center line at a distance Q, approximately equal to 0-.14'7Dbelow.

the horizontal line. Then with O as a center and with radius S approximately equal to 0.384D, draw the arc 2a intersecting and joining the arcs 3a. The are 2a corresponds to the bottom '2 of the trough. The result is the compound curve shown by the solid line 1a. It is not a true ca-tenary, because it. is drawn about three-fixed centers. a

The curve above described was originally determined empirically. A semicircular sheet metal trough of standard weight was loaded untilit showed, by actual measurement, itsmaximum deflection. Thismaximum deflection, indicated in Fig. 2 by the broken line e, occurred when the trough was between one-third and one-half full of Water. As the load was increased, the deflection decreased, until, when the trough was loaded to maximum capacity, the measured deflection was as shown by the broken line f. Upon reducing the load, the measured deflection firstincreased to the broken linee, and then subsequently decreased,'but never fell belowthe broken line 1 even when the trough was empty, the metal having received a permanent set which prevented it from returning closer to semicircular form than the maximum load curve 1. The curves e and 1 therefore represent the limits of deflection or distortion to which the trough is subjected under all conditions of varying load. When these limits were determined and plotted as the curves e and f, 'a curve representing a mean was drawnbetween them, and this meanithe curve 1a) wasfound to be formed almost exactly about the three centers'O and 0, whose positions, as well as the radii Rand S of the compound curve,- could be expressed in terms of the diameter D.

It will be apparent that, by initially forming my trough' to the compound curve described above, I have not only eliminated entirely the major distortion from semicircular form which occurs upon the initial-loading of the fiume, but I have also reduced by'fifty per cent the elfects of the subsequent distortion due to variations in load.

My flume,having an initial and natural (1. ,e.

which is a negligible factor in causing leaks and deterioration; Moreover, there is no appreciable variation with changes in load in theinclination of the upper portions of the trough sides 3 and suspension rods 4;, so that bending of said rods, at their points of attachment tothe frame, is

reduced to a negligible quantity.

My improved method of forming the trough to the above described curvature consists in first rolling a flat'sheet throughout its entire width to thejcurvature of the greater radius R, as illustrated Fig; 3, wherein 7 indicates any suitable rolling instrumentality, 8 is the position and path of theincoining flat sheet, and 9 is the formed sheet curved throughout its width to the radius R. The edges of the arcuate sheet are then grasped by any suitable clamping means indicated at 10 inFig. Land are forced toward each other until said edgesare the desired distance D apart. The bottom of the trough will then have a curvature of radius S, assuming such curvature by natural bending resulting from forcing its edges together.

7 It will be seen' that this process is extremely simple and inexpensive, involving as it does only one rolling operationupon an arc of constant radius, and one subsequent bending operation,

both of which can be done with the simplest form .of apparatus.

Starting with the known width D across the top of the trough, a sheet is provided whose width is equal to the semicircle upon D as its diameter, or 1.5708D. Using the formula hereinbefore described, the bending rolls '7 are set to produce an are having the radius R or 0.834D; Then'the edges of the arcuate sheet are brought toward each other until they are separated by the distance D,whereupon the central portion of the sheet, forming the bottom of the trough, will automatically assume an arc of radius S. Therefore the only values which need be known; in the practical operation of forming the trough, are its width D, the width of the sheet,'

1.5708D, and the radius R, 0.834D.

Theabove described method of forming the trough will provide smalltransition areas 11 between the sides and bottom where the radius changes from Rto S; that isto say, the radius of the formed trough does not change abruptly from R to S, as in the mathematical layout shown in Fig. 2. I These transition areasare so narrow, however, as to be negligible for all practical purposes, and as they occur at the points g of Fig. 2, where the curves of maximum and minimum deflection e and cross, they'have no effect upon the value of the curve 1a as a mean between said maximum and minimum. v i

Obviously, the sides 3 of theltrough may be extended upwardly to providefa'free-board above the maximum water line, to'prevent spilling at its curves in the 'flume or as a result ofwaves, and

such free-board portions of the sides may be either straight and curved,as desired, since they are not affected by the loading of the flume. When such free-boards are; provided, either straight or curved upon a radius'other than. R, the basic width D is the width across the 'flume at the maximum water level, and the width of thesheet must be increased by'the sum of the widths of the free-board portions. That portion of the sheet below the maximum water level or width line D is treatedexactly as hereinbefore described.

The numerical values: stated herein for the radii R and S and the oo-ordinates 'ofthe centers 0 and O are those which give best results under average conditions; Obviously, however, it ma its across the top or the finished trough, and said radius being equal to 0.834 times said diameter; and then further bending the central portion of the sheet to a radius equal to 0.384 times said diameter.

2. The method of forming a sheet metal trough to compound cross sectional curvature which consists in first bending a sheet laterally to a curvature of constant radius, the width of the sheet being equal to one half the circumference of a circle whose diameter is the desired width across the top of the finished trough, and said radius being greater than the radius of said circle; and then further bending the central portion of the sheet to a curvature whose radius is less than the radius of said circle.

3. The method of forming a sheet metal trough to compound cross sectional curvature which consists in first bending a sheet laterally to a curvature of constant radius, said'radius being equal to 0.834 times the desired width across the finished trough at its maximum water level, and then further bending the central region of said sheet to a curvature whose radius is 0.384 times said width. 1 a

4. The method of vforming a sheet metal trough to compound cross sectionalcurvature which consists in first bending a sheet to a curvature of v constant radius, said radius being greater than one half of the desired width of the finished trough, and then further bending the centralpor- -tion of the sheet to a curvature whose radius is less than one half of said desired width, the side portions of the trough remaining at substantially the first mentioned curvature.

5. The method of forming a sheet metaltrough'.

to compound cross sectional curvaturewhich con-' sists in first bending a sheet to a curvature of constant radius, said radius being greater than one half of the desired width of the finished trough, and then applying pressure directly to the edge portions of said sheet to force them togetherto j ia 

